Not a typical VS V6 engine noise (Think lots of crickets from the engine).

[-=ApheX=-]

Howdy Commodore Forum!,

Firstly a brief history; My pride and joy is a typical VS V6 with 170,xxx on the clock. I'm the second owner, the original owner was an older gentleman!
This car had been babied all it's life and since I've had it going on 6 months now, has continued to be babied.
I've serviced, cleaned, replaced etc all the typical things you'd do to a car this age despite it been very well looked after its entire life.

Anyway during these hotter 40 something degree days I've started to hear that typical ecotec lifter and rocker ticking noise more and more and getting louder and louder. So I thought ok then, fair enough, some lifter free up and then an oil change with primo oil a little later on should reduce that noise!.
FYI This is not a ticking noise question...

So this is where my issue begins.

Days later I took a "cruisey" drive from Bendigo to Melbourne (not smashing the 120 or 130km/h mark at all.) with out an issue. Hours later during the ride home along the highway, I hear what could only be described as a large number of crickets humming or chirping quite loudly (the same kind you'd hear late at night), reverberating through the car???
I Immediately thought maybe one of my wheels might be causing this vibrating sound so pulled into the nearest servo for a closer look. All my tires were fine.
Then whilst the car was idling I head the noise start again, this time more directly coming from the engine... It was incredibly hard to pin point with out tools and such so I decided it must be a bearing starting to give out.

**Also please note that before it's mentioned, I've considered that using the lifter free up solution i may have disrupted some carbon deposits and potentially blocked an oil channel? and although i've read bits and pieces about using diesel oils and so on to do an internal clean i'm not yet ready to believe one bottle of that being used on a lower Km engine could disrupt carbon deposits that I "personally" believe to be an issue of a much higher and ill treated engine??? Plus the noise wouldn't seem consistent of a blocked oil channel? however I'm certainly not an expert with that one!

Anyways long story short,
I've replaced all pulleys, the tensioner arm assembly, alternator, vacuum hoses that sit in and around the plenum and serpentine belt. All haven't worked. (I have considered that it could be the waterpump giving out, but this sound cannot be narrowed down to this part. The same goes for the harmonic balancer which I checked and double checked and it seems well with in healthy limitations)... Anyway.

Later a friend lent me his stethoscope which frustratingly couldn't accurately pin point this noise but it sounded loudest around the thermostat? so I changed it and still no result... FYI. I tried the long screw driver trick against potential problem parts to get a closer pinpoint to the noise and it also indicated the same area.

So I've now broken it down to what it could now only be? maybe a timing chain issue, an oil pump issue, stuffed injector(s) and even a PCV valve issue! However this noise and the issue it could be attributed to cannot be located without blindly replacing more parts. I fear the worst that maybe the oil pump, timing chain or even the cam and or pushrods etc are at fault or are failing??? I've reached the point of what I know I can do and fix on my car before giving up and taking it to a mechanic...

Please if anyone knows what I'm referring to or is even familiar with this noise I'm speaking of please let me know what it was in your situation and what was done for it to be fixed?

Thanks for your time and your help is greatly appreciated.
Cheers.

 

[SavVYute]

Have you tried running the engine with the belt off?
Just for a short time to rule out the water pump as the issue.

 

[VPRob]

Can't help with the noise except to suggest using a short (!m) length of garden hose as a sort of stethoscope. One end to ear (obviously) and point the other end towards potential sources of the noise. It isolates noises quite remarkably and may help locate the source. Good luck with it.

 

[Wozza]

as above run with out belt for a few min..if the noise go's then check the water pump for leaks and that it rotates smoothly with no up/down left/right movement...same for the power steering pump though they tend to groan and wine when dying...Also the aircon pulley they can get noisy, as a quick fix for aircon just get a belt for a non aircon VS and run that.....
if the noise is still there with the belt off record a sound or video file and post on youtube or some other hosting site...

 

[hako]

Check your exhaust manifold (both sides) for any breaks in the gasket or tiny cracks, also where the O2 sensors attach......look for rusty streaks indicating leaking exhaust gases...do this all the way to the cat.
Exhaust leaks from tiny cracks/splits can sound like someone crumpling paper or a crackling noise.

Good Luck.

 

[-=ApheX=-]

Thanks for your replies fellas! I did in fact forget to mention that I did try that belt removal trick to no avail...
Even just now as i've only come back inside from scratching my head staring at the engine whilst its making this noise can I conclude that the noise is almost defiantly coming from around the plenum.
And thanks for the advice VPRob, i've used various methods of trying to narrow the location of where this sound could be originating from. The best I can tell you is that it almost sounds like it reverbs through the entire top part of the engine whilst it's running, hot or cold!
In fact just now whilst again trying to find this stupid noise, it almost sounded like just one injector starts pulsing stupidly fast and then the noise calms down and disappears and until it decides to do it again. but of course the engine runs fine during the noisy episode?
I know that some or all of this may not be making much sense... I'll try and get a video linked up this evening so that you guys can get a better idea of what this may actually be?
Cheers Guys!

*Edit, Thanks for your advice also Hako, I considered that it could be originating from the exhaust, I pulled up along side a large brick wall in a parking space in town, this sound started again and it was being amplified off the wall back to me and honestly at that point I thought perhaps a poor seal between the Y piece and the Cat, I will actually get back under it once it cools a little and double check all your suggested points.
Thanks Again.

 

[EYY]

Is it noisy at the back of the engine behind the manifold too? Might be the balancer shaft bearings.

 

[-=ApheX=-]

Well kinda? its a very strong noise from the front of the engine, say if i put a screw driver to the thermostat housing it's very loud, however, putting it on the water pump i get nothing, under the plenum behind the injectors, well sort of, honestly it's the most bizarre thing I have ever encountered in my life of driving and self servicing cars!
Sorry for the vague answer EYY
** Edit... My understanding with the Balancer Shaft and it's bearings they are generally prone to noise and vibration in gear usually in a 3rd or 4th gear? Could it be possible for such a noise to occur idling cold or hot, under no load at all?

 

[hako]

The balance shaft just thumps and rattles a bit when the bearing is worn, is noticeable at idle but hardly likely at your mileage although anything is possible.